The cardiovascular health of U.S. children is strikingly dismal, so says a new statement from the American Heart Association.

Specifically, less than 1 percent of American children meet the organization's definition of ideal cardiovascular health, according to statement author Dr. Julia Steinberger, a professor in pediatrics and director of pediatric cardiology at the University of Minnesota in Minneapolis.

Poor diet is the biggest contributor to this trend, Steinberger says. "Unhealthy diet was shown to be present in greater than 90 percent of American children," she explains. The next factor is low levels of physical activity.